1. Field of the Invention
The present invention relates to a method of treating dyed polyamides to minimize ozone fading thereof. More particularly, the invention relates to a method of treating dyed polyamides with a substituted piperidine thiourea derivative so that the dyed polyamide, particularly one dyed with a disperse dyestuff, will have minimized or reduced ozone fading without a reduction in light stability.
2. Discussion of the Prior Art and Other Information
Salvin and Walker reported in 1955 the phenomenon of ozone fading of dyes in fiber. Textile Res. Journal, Vol. 25, p. 571. Since that time it was determined that nylon fibers dyed with disperse dyes, particularly Disperse Blue 3, C.I. No. 61505 are quite susceptible to ozone fading when the dyed fiber is subjected to high temperatures and humidity.
Ozone is ordinarily present in air at sea level at concentrations of about 1 to 5 parts per one hundred million. Although ozone is present in this extremely low concentration, a disperse dyed fiber will undergo severe ozone fading if the humidity in the atmosphere is high enough, i.e., over 75% relative humidity.
Various attempts have been made to overcome the problem of ozone fading by using certain disperse dyes. However, this technique is not always effective and can give rise to other problems such as increased processing costs and unlevel dyeing. A search has been undertaken to develop chemicals known as antiozonants to improve the dye ozone fastness of polyamides. While some chemicals improve the ozone fastness of polyamide fibers, many of the chemicals greatly reduce the light stability of the fibers. These chemicals include 4-benzylthiosemicarbazide, 4-t-butylthiosemicarbazide, 4,4-dimethyloxazoline-2-thiol, 1-(2-hydroxyethyl)-3-methylthiourea, 1-t-butyl-3-(2-hydroxyethyl) thiourea, 1-(2-hydroxyethyl)-3-phenylthiourea, 1-n-butyl-3-(2-hydroxymethyl-2-propyl)thiourea, 1-(1,3-dihydroxy-2-methyl-2-propyl)-3-phenyl-thiourea, 2,5-bisoctyldithio-1,3,4-thiodiazole, 2,5-dimercapto-1,3,4-thiodiazole, N,N-diethylthiourea, 2,4-dihydroxybenzophenone, 4-dodecyloxyhydroxybenzophenone, 2,4-dimethylbenzophenone, t-butyl-diethanolamine, a mixture of tannic acid and tartar, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid, and oxalic anilide.
A list of various gas fade inhibitors, including symmetrical diphenyl substituted thioureas, appear in the American Dyestuff Reporter, May 12, 1952 at page 300 as part of an article by Salvin et al. entitled "Advance in Theoretical and Practical Studies of Gas Fading." The article states that the fiber and the dye both play a part in gas fading caused by nitrogen dioxide.
U.S. Pat. No. 3,822,996 to Lofquist et al teaches the use of a water-soluble thiourea for coating dyed nylon fibers to give an improved resistance to ozone fading. The water-soluble thiourea is a saturated alkyl substituted thiourea having less than 5 carbon atoms such as dimethyl thiourea, trimethyl thiourea, and N-methyl thiourea.
Various polythioureas to inhibit ozone fading of dyed polyamides are disclosed in U.S. Pat. No. 3,917,449 to Wells et al. These compounds have the general formula ##STR2## where x and y are 0, 1, or 2, R is a difunctional aliphatic hydrocarbon radical or ##STR3## where Z is H or ##STR4## R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are independently selected from phenyl or a monofunctional allyl or alkyl radical of 1 to 12 carbon atoms, R.sub.5 and R.sub.6 are ##STR5## R.sub.7 and R.sub.8 are independently H or monofunctional ally or alkyl of 1 to 12 carbon atoms with the proviso that when x=0 and R.sub.1 and R.sub.2 are allyl, R has to be a difunctional fatty acid residue of 24 to 108 carbon atoms or a difunctional alkyl substituted cyclic aliphatic hydrocarbon.
U.S. Pat. No. 3,705,166 to Murayama et al. discloses acrylic acid derivatives of 2,2,6,6,-tetramethyl-piperidines useful as stabilizers for the photo- and thermal deterioration of various synthetic polymers, including polyamides.
U.S. Pat. No. 3,828,052 to Holt et al describes acylhydrazone derivatives of 2,2,6,6,-tetramethyl piperidine-4-one as stabilizers of organic materials. The derivatives are said to be particularly worthwhile to stabilize polyolefins against the effects of ultra-violet radiation. The derivatives are said to be generally light stabilizers.
U.S. Pat. No. 3,584,993 to Myles et al. shows alkylene bis-allyl thioureas as stabilizing agents for disperse dyes and nylon. The thioureas are generally nitrogen substituted N-allylthioureas.
U.S. Pat. No. 3,904,581 to Murayama et al. relates to the stabilization of synthetic polymer against photo and thermal deterioration by incorporating various alkyl substituted piperidines therein.